E. Sirvet et al. U.S. Pat. No. 3,766,851 issued Oct. 23, 1973 for Continuous Can Printer and Handling Apparatus describes relatively high speed apparatus for applying decorations to the exterior of cylindrical containers while they are mounted on mandrels disposed along the periphery of a large rotating wheel-like carrier. In continuous can printer apparatus of this type, means are provided to assure that when a mandrel moves through the decorating zone along a normal path for printing, such mandrel is properly loaded with cylindrical container. If a particular mandrel is empty or is loaded improperly, such mandrel is moved away from the path for printing to a no-print position wherein neither an empty mandrel nor an improperly loaded container will engage the printing blanket. Examples of prior art means for retracting unloaded and misloaded mandrels to a no-print position are disclosed in J. P. Skrypek et al. U.S. Pat. No. 4,140,053 issued Feb. 20, 1979 for Mandrel Mounting and Trip Mechanism For Continuous Motion Decorator and R. DiDonato et al. U.S. Pat. No. 5,111,742 issued May 12, 1992 for Mandrel Trip Subassembly For Continuous Motion Can Decorator.
In the aforesaid U.S. Pat. No. 4,140,053 each mandrel is part of a subassembly that is mounted on a pivot axis to a continuously rotating carrier. When an unloaded or misloaded mandrel is detected a linear actuator acting through a crank and an eccentric moves the pivot axis for the entire subassembly and in so doing moves the unloaded or misloaded mandrel away from its normal or print path so that neither the mandrel nor a misloaded container will engage the printing blanket. While this type of mechanism operates well at high production rates, say 1200 cans per minute, mounting and dismounting of the subassembly from the carrier is time consuming and adjustments must be made while the subassembly is mounted on the carrier.
In accordance with the aforesaid U.S. Pat. No. 5,111,742, the mandrel tripping actuator and mandrel are combined in a subassembly that may be adjusted when the subassembly is dismounted from the carrier. In particular, this subassembly includes a base with a rotary actuator thereon, which actuator is powered directly by a non-mechanical source of energy, preferably pressurized air. The actuator includes a rotor having an extension on which the mandrel is rotatably mounted. The mandrel axis is slightly offset laterally from the rotor axis so that limited pivoting motion of the latter causes the mandrel to move between a normal radially outward print position and a radially inward trip or no-print position. Two guide rods extend from the base and are received in radially extending guide channels of the carrier to removably mount the subassembly on the carrier and guide the subassembly radially in accordance with dictates of a stationary cam track cooperating with a cam follower that is part of the subassembly.